This invention relates to a drive apparatus for a cycle. This invention also relates to a cycle when provided with the drive apparatus.
In GB-A-2326856 we have described and claimed drive apparatus for a cycle. The drive apparatus described in GB-A-2326856 comprises an electric motor, a first pulley which is driven by the electric motor, a second pulley, an endless belt which passes around the two pulleys and which is driven by the first pulley, and mounting means for mounting the drive apparatus to the cycle. The drive apparatus is such that during use the endless belt is in driving engagement with a tire of a wheel of the cycle. The mounting means is a swinging link mounting means.
It is an aim of the present invention to improve upon the drive apparatus described in GB-A-2326856.
Accordingly, the present invention provides drive apparatus for a cycle, which drive apparatus comprises an electric motor, a first pulley which is driven by the electric motor, a second pulley, an endless belt which passes around the two pulleys and which is driven by the first pulley, and mounting means for mounting the drive apparatus to the cycle, the drive apparatus being such that during use the endless belt is in driving engagement with a tire of a wheel of the cycle, the mounting means being such that it is a swinging link mounting means which enables the distance between centers of the first and the second pulleys and the tire to vary during use of the drive apparatus and thereby to enable the drive apparatus to exert on the tire a varying contact pressure which increases as transmitted torque increases, the swinging link mounting means comprising attachment means for attaching the drive apparatus to the cycle and pivot means about which the electric motor, the first pulley, the second pulley and the endless belt pivot, and the drive apparatus being characterised in that the electric motor, the first pulley, the second pulley and the endless belt form transmission means which is counter-balanced about the pivot means such that in an equilibrium position the endless belt is not in contact with the tire when the drive apparatus is not in use.
The drive apparatus may be one in which the transmission means is counter-balanced such that in the equilibrium position the endless belt is not more than 10 mm from the tire. Any suitable and appropriate distance may be employed.
The transmission means may be counter-balanced about the pivot means by having equal masses acting on either side of the pivot means. This ensures that jolt-induced accelerations due to road conditions act to create equal forces on either side of the pivot means. There is therefore no moment created due to bumps and the transmission means is able to remain undisturbed with the endless belt remaining slightly away from the tire if there is no power being transmitted, or remaining in contact with the tire if power is being transmitted.
As used, the drive apparatus will include a battery for the electric motor. The weight of the battery is advantageously used as a counter-balance for the weight of the transmission means. Thus the battery may be regarded as a counter-balance for the transmission part of the drive apparatus formed by the electric motor, the first pulley, the second pulley and the endless belt.
Advantageously, the battery acts on an arm which forms a short moment arm. This allows the drive apparatus to be designed such as to be extremely compact. A compact design for the drive apparatus is especially desirable for aesthetic reasons, for mounting reasons, and for space-saving reasons.
The mounting means may comprise a first attachment arrangement for attaching to handlebars or a handlebar stem tube of the cycle, and a second attachment arrangement for attaching to another part of the cycle below the handlebars.
The first attachment arrangement may be at least one clamp.
The second attachment arrangement may be for attaching to a head tube of the cycle. Alternatively, the second attachment arrangement may be for attaching to front forks of the cycle, or a brake assembly of the cycle. Irrespective of where the second attachment arrangement is attached, it may be at least one clamp.
The drive apparatus is preferably situated above a front tire of the cycle such that a line passing through a center of rotation of the second pulley and the pivot means passes between the first mounting point and a seat of the cycle. The line is a line of force and the effect of this line of force is to create a moment that pushes the drive apparatus down against the tire. This moment is resisted by the second attachment arrangement.
Advantageously, the drive apparatus includes a belt reduction gearbox from the electric motor. The belt reduction gearbox operates quietly. If desired, a spur gear reduction gearbox may be employed but this will generally be noisier than the belt reduction gearbox.
The drive apparatus may include a housing for the electric motor, the first pulley and the-second pulley. In this case, the drive apparatus may include an electric power on/off switch positioned within the housing.
The drive apparatus may include link means between the on/off switch and handlebars of the cycle, the link means comprising a length of metal which has a first end for activating the on/off switch and which has a second end positioned below and adjacent handlebars of the cycle for being gripped and pulled by a cyclist. Pulling the second end up will cause the on/off switch to go to its on condition and thus the electric motor will start. Letting the second end go will cause the on/off switch to go to its off condition and thus the electric motor will stop.
The drive apparatus may include dampening means for dampening oscillations of the transmission means relative to the housing.
The dampening means may include an elastic band. Any suitable and appropriate type of dampening means may be employed.
The drive apparatus may include a recess for receiving a mains charger for charging the battery. The drive apparatus may be manufactured and sold with the mains charger.
The drive apparatus may be one in which the second pulley is nearer to the swinging link mounting means than the first pulley.
The housing may have an aperture for receiving a security device for stopping theft of the drive apparatus from the cycle.
The electric motor may be provided with an electric current and temperature limiting device for avoiding overloading of the electric motor such as would generate sufficient heat to damage the electric motor.